Purchased a spare power adapter for a Dell Inspiron laptop and now the spare adapter and original adapter will not charge the laptop

First thought is the battery is bad. If you replace the battery and the problem still exists then it is in the charging circuit

some times the knock off adapters will not be detected properly, and will not charge the batteries, only powering up the laptop. But if you say the power adapter you have purchased was from Dell, then it definitely should be a genuine Dell product. Are you confident that the old adapter was charging the battery before you plugged in the new one?  You can check in the bios to see if both adapter are detected properly and if they are actually charging the battery.  What is the percentage of charge of the battery, maybe the battery is already fully charged, you can see the stats in the bios.   You can also run diagnostics on the charging system. Turn off the laptop, then turn it on and then start tapping the f12 key as soon as you see the Dell logo, then in the menu select diagnostics. The diagnostics should run tests on the charging system.
when the user plugs the ac adapter into the laptop does the plug seem loose? If so it may be a bad connector and that would need to be replaced.

It's common for charging ports to be damaged where they connect to the motherboard.  The thin copper traces on the PCB won't take much flexing before they break.

If this is the situation, then it can be diagnosed by attaching the known-good original adapter, then slowly wiggling the power cord connector where it enters the case.  If the charge light flickers, the charging port is damaged.

Diagnose the battery by taking it to an identical laptop, plugging it into that one, and see what the second laptop has to say about the battery.

Another power adapter from an identical computer does not charge the laptop.  Here is another thing the user told me:  He said that the computer is plugged in and at 85%.  The battery stays at 85% and does not go down or up.  It has been like this for the past 2 hours.

The battery is probably reaching the end of its life, once the battery does not fully charge then you know that the battery needs to be replaced soon.  As this is a typical symptom it will not fully charge.  That goes for even Cell phone batteries as well, when it takes for ever to charge to 100 percent, or if the charge does not last long you know that battery is reaching the end of life. Read the following articles about the battery life in your computer: https://www.cellphonerepair.com/signs-replace-your-laptop-battery/   and this article that talks about a utility to test your battery life: https://www.howtogeek.com/172362/how-to-know-when-its-time-to-replace-your-laptops-battery/
and finally  to download the battery utility: http://www.nirsoft.net/utils/battery_information_view.html

Forgot to mention this is a brand new computer. 1 week old

return it as defective.